The technical portion of the profession of an optician consists in mounting a pair of ophthalmic lenses in a frame selected by a wearer. Mounting comprises three main operations:                acquiring the shape of the bezel of each of the two rims of the eyeglass frame selected by the future wearer, i.e. the shape of the longitudinal strand of the corresponding bezel, generally corresponding to the bottom of the groove going round the inside of the rim of the frame;        centering each lens, which consists in determining the position each lens is to occupy in the frame so as to be appropriately centered facing the pupil of the wearer's eye so that the lens acts appropriately in performing the optical function for which it was designed; and        machining each lens, which consists in cutting its outline to the desired shape, while taking account of defined centering parameters so that it can be fastened to the corresponding eyeglass frame.        
The present invention relates to the third operation of machining ophthalmic lenses. This is performed by means of an appropriate machining device.
In order to cut the outline of the lens to the desired shape, various machining operations are performed one after another on the lens. After an operation of edging the lens to shape its periphery, various finishing operations are performed on the edge face of the lens.
In particular, if the lens is to be engaged in a rimmed eyeglass frame, finishing includes a beveling operation that consists in making a bevel on the edge face of the lens, i.e. a peripheral ridge that is shaped to have a generally V-shaped section. The bevel is designed to engage in the bezel of the corresponding rim of the frame for the purpose of fastening the lens. If the lens is to be mounted in a drilled eyeglass frame, finishing includes a drilling operation that consists in making bores or notches in the lens for having the eyeglass frame fastened thereto. If the lens is to be mounted in a half-rimmed eyeglass frame, finishing includes a grooving operation that consists in forming a groove in the edge face of the lens, which groove is suitable for receiving a string for attaching the lens to the frame.
Document EP 1 807 244 discloses a device for machining ophthalmic lenses, which device is suitable for implementing all of the above machining operations with the help of various machining tools. That machining device includes shafts for supporting the ophthalmic lens, a grindwheel for shaping and beveling the lens, and a finishing module.
To enable the lens to be moved towards or away from the shaping and beveling grindwheel, the clamping shafts are carried by a rocker that can pivot about an axis parallel to the lens support axis.
To enable the lens to move towards or away from the finishing module, the finishing module includes a support that is pivotally movable about an axis parallel to the lens support axis.
To perform additional machining on the lens (drilling, grooving, polishing, and finishing), the support of the finishing module carries a set of finishing wheels that are mounted to rotate about an axis of rotation, and also a drill that is movable in pivoting on the support about an axis that extends transversely relative to the lens support axis. The drill carries a drill bit that is mounted to rotate about a second axis of rotation that can be oriented relative to the lens because the drill is free to move appropriately.
The main drawback of such a machining tool is that the set of wheels comprises numerous tools that are stacked one next to the other so that the set of wheels is cantilevered out over a long length. While the lens is being machined, bending forces are applied to the set of wheels, thereby deforming it and causing the machining of the ophthalmic lens to become inaccurate.
Furthermore, because of its length, the set of wheels occupies a considerable amount of space and, because of the way the tools are stacked together, it requires time-consuming maintenance. In particular, in order to change a single one of the tools in the stack, it is necessary to begin by removing all of the tools that precede it in the stacking order.
Furthermore, the set of wheels is driven in rotation by a common motor, which means that it is necessary to modify the speed of rotation of the motor depending on which tool is being used. The motor is thus caused to operate over a range of speeds of rotation that correspond to powers that are far removed from its nominal power curve. As a result, it is necessary to use a motor that is powerful, and that is therefore expensive and bulky.
Furthermore, since the drill can move relative to the finishing module, it is essential to provide a motor for driving the drill bit in rotation and a motor for driving the set of wheels in rotation. In addition to its high manufacturing cost, such an architecture gives the finishing module size and weight that are considerable.
Finally, only the drill bit can be oriented relative to the lens, which means in particular that it is not possible to modify the orientation of the groove in the edge face of the lens.
Document FR 2 614 227 discloses a machining device in which provision is made to group together various machining tools on a common module, the tools having axes of rotation that are distinct and parallel to the axis of the lens support. In order to select each tool (by placing the selected tool so that it faces the lens for machining), that module is mounted to pivot about an axis that is parallel to said axes of rotation. Nevertheless, that device does not have a drill tool. The above-mentioned pivoting also prevents the machining tools from being inclined relative to the lens, e.g. for the purpose of modifying the orientation of the groove in the edge face of the lens.
Even assuming it might be envisaged to combine the teaching of the two above-mentioned documents, that would not lead to a device that is fully satisfactory and functional. Supposing it were envisaged to add an additional tool against the drill of the machining device described in document EP 1 807 244, e.g. a grooving tool, even though no document in the prior art proposes that expressly, there would be remain a problem of providing motor drive for those two tools. The use of two motors would lead to problems of motorization and of weight. The use of a single motor would mean that advantage could not be taken of the full power of the motor when drilling or when grooving the lens. It would therefore be necessary to use a motor that is powerful and thus expensive and bulky. In addition, placing those two tools beside each other would lead to interference appearing between the tools and the lens support shafts, which would make it difficult for the drill bit to have access to the central portion of the lens. Because of such interference, it would then be impossible, or at least difficult, to drill lenses close to their geometrical centers, and that can be problematic with lenses of small dimensions.